Using vast discrepancies between environmental assessments by the Obama and Trump administrations related to the Clean Water Act (CWA) as a key example, authors of this Policy Forum highlight the need for a systematic protocol for government cost-benefits analyses of proposed regulations. This example is particularly timely given that the CWA will be the focus of a U.S. Supreme Court (SCOTUS) hearing set for October 11. In 2015, U.S. President Obama extended the CWA, which protects waterways, to include previously unprotected areas, including wetlands. This decision was based on a regulatory impact analysis (RIA) completed by the Environmental Protection Agency and the Army Corps of Engineers. However, when U.S. President Trump ordered a second RIA in 2017, it found nearly opposite results. According to Kevin Boyle and colleagues, the 2017 RIA's assessment of "wetland" benefits includes improper descriptions and even omits entire categories of costs and benefits. What's more, the 2017 RIA excludes studies prior to 2000, but best practice in current economic literature requires valid reasoning as to why studies do not meet current criteria, which the 2017 RIA does not provide. The authors say timely implementation of a standard protocol is imperative as agriculture, road construction and maintenance among other programs under the CWA will be affected by the SCOTUS' ruling on October 11. The major differences highlighted in this Policy Forum underscore the need for government agencies to base their economic analysis of regulations on credible science, the authors say, noting that such measures will lead to better decision-making related to human health and the environment.